Radiation sensitive remote control system

ABSTRACT

A remote control system has a control for effecting a first control function in response to sensed incident light which has a first quality of polarization, and a second control function in response to sensed incident light which has a second quality of polarization. A projecting arrangement directs a beam of light away from polarized light-sensing means connected to the control, and a portable remote unit includes a reflector for directing the light beam to the sensing means, and light polarizers for selectively imparting on the light beam the mentioned first quality of polarization and alternatively the mentioned second quality of polarization.

United States Patent [54] RADIATION SENSITIVE REMOTE CONTROL SYSTEM 20Claims, 7 Drawing Figs. [52] US. Cl. 250/225, 250/216, 250/206 [51] Int.Cl G02f 1/18 [50] Field of Search 250/225,83.3lR,2l6,206,203;356/114,116,117,118 [56] References Cited UNITEDSTATES PATENTS 2,140,368 12/1938 Lyle 250/225 CONTROL 2,167,484 7/1939Berry 250/225x 2,362,832 11/1944 Land"... 2so 225x 2,651,771 9/1953Palmer 2s0/225x 2,993,997 7/1961 McFarlane... 250/225x 3,158,675 11/1964MurrayetaL. 356/116 3,502,888 3/1970 Stites 250/219 PrimaryExaminer-Walter Stolwein Attorney-Luc P.Benoit ABSTRACT: A remotecontrol system has a control for effecting a first control function inresponse to sensed incident light which has a first quality ofpolarization, and a second control function in response to sensedincident light which has a second quality of polarization. A projectingarrangement directs a beam of light away from polarized light-sensingmeans connected to the control, and a portable remote unit includes areflector for directing the light beam to the sensing means, and lightpolarizers for selectively imparting on the light beam the mentionedfirst quality of polarization and alternatively the mentioned secondquality of polarization.

PATENTEDuuv 2 1971 3,617, 761

sum 1 OF 2 INVENTOR. v flfxrae P Coo/255k,

BACKGROUND OF THE INVENTION 1. Field of the Invention The subjectinvention relates to remote control systems and, more particularly, tocontrol systems which are operated from a remote location through theagency of radiant energy.

2. Description of the Prior Art There exists a continuing need forremote control systems which dispense with the necessity of wiresbetween the control signal receiver and the remote control unit.

Prior-art wireless remote control systems typically employ small radiotransmitters, polarized, modulated or standard light sources orultrasonic generators at the remote control unit. This raises one ormore of the following disadvantages: necessity of power source or poweroutlet at the remote location, requirement of complex signal detectionequipment at the control signal receiver, vulnerability to environmentalinterference, or generation of interference.

Background material for an improved remote control system may be foundamong signaling, communications, ranging and object identificationsystems that employ retrodirective reflectors at a remote location.However, a prior-art signaling system that employs a corner reflectorwhich is selectively obscured by a shutter is directed to visualsignaling and is thus not sufficiently developed for present purposes.Similar considerations apply to a prior-art voice communication systemthat employs -a corner reflector having a vibratile element formodulating a light beam with acoustical intelligence, and to prior-artranging systems in which retrodirective reflectors with fixed 'ormovable elements constitute the target to be located. A prior-art objectidentification system does use polarization phenomena to excludespurious reflected signals, but relies on color codes to distinguishbetween different objects. This implies operation in the visible rangeof light, which is objectionable in those many applications in which thepresence of a visible light beam is undesired.

SUMMARY or THE INVENTION The subject invention overcomes or materiallyalleviates these disadvantages by providing a remote control systemcomprising means for sensing incident light having a first quality ofpolarization and incident light having a second quality of polarization,control means connected to said sensing means for effecting said firstcontrol function in response to sensed incident light having a firstquality of polarization, and a second control function in response tosensed incident light having said second quality of polarization, meansfor projecting a beam of light in a direction away from said controlsensing means, and a portable remote unit. including means forreflecting said beam of light to said sensing means and means combinedin said remote unit with said reflecting means for selectivelyimpartingon said beam of light said first quality of polarization andalternatively said second quality of polarization.

Since the remote unit operates on a projected beam of light, no powersource or outlet is required at the remote location. Control means whichdistinguish between qualities of light polarization may be of relativelysimple design, including uncomplicated photocells and polarizationfilters. Vulnerability to environmental interference is inherently lowin a polarized light system, since environmental light is typicallydepolarized. Systems which operate with directed light beams also are oflow interference generation, and any annoyance by the light beam can beavoided by the use ofinfrared or other invisible radiation in accordancewith a preferred embodiment of the invention.

From another aspect thereof, the invention resides in a remote controlsystem comprising means for sensing incident light having a firstquality of polarization and incident light having a second quality ofpolarization, control means connected to said sensing means foreffecting a first control function in response to sensed incident lighthaving said first quality of polarization, and a second control functionin response to sensed incident light having said second quality ofpolarization, means for projecting in a direction away from said controlmeans a beam of light polarized in a predetermined plane, and a portableremote unit including means for reflecting said polarized beam of lightto said control means and means combined in said remote unit with saidreflecting means for selectively realizing in said reflected beam oflight said first quality of polarization and alternatively said secondquality of polarization.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a frontal view of a firstreflector device useful in the practice of the subject invention;

FIG. 2 is a frontal view of a second reflector device useful in thepractice of the subject invention;

FIG. 3 is a diagrammatic view of a remote control system in accordancewith-a preferred embodiment of the subject invention;

FIG. 4 illustrates a particular phase of operation of the system shownin FIG. 3;.

FIG. 5 is a perspective view of a remote control unit in accordance witha preferred embodiment of the invention;

FIG. 6 is a diagrammatic view of a modification of the control system ofFIGS. 3 and 4, in accordance with a further preferred embodiment of thesubject invention; and

FIG. 7 is a diagrammatic view of a further modification of the controlsystem of FIGS. 3 and 4, in accordance with yet another preferredembodiment of the invention.

DESCRIPTION OF PREFERRED EMBODIMENTS FIGS. 1 and 2 depict retrodirectivereflector devices that may be used in the practice of the subjectinvention.

More specifically, FIG. 1 illustrates a corner reflector 10 having threereflective surfaces l2, l3 and 14, each of which extends at right anglesto the other two reflective surfaces. As is well known, a cornerreflector is retrodirective in that it returnsincident beams of light totheir origin. Corner reflectors may, for instance, be cast in glass ortransparent organic materials or formed of highly reflecting aluminum,in accordance with conventional prior-art techniques.

FIG. 2 illustrates a retrodirective reflector 16 in which a layer ofglass beads 17 is retained by an adhesive 18 on a matte white substrate20. Arrangements of the type shown in FIG. 2 are of widespread use inmotion picture and still projector screens, and in traffic signs andvehicle markings.

The particular use of the devices of FIGS. 1 and 2 will be explained asthis description proceeds. At the present'juncture, the remote controlsystem 23 shown in FIGS. 3 and 4 will be considered.

The system 23 comprises a base station 24, and a remote control unit 25.The remote control unit 25 may be of a handheld type. A lamp 27, with areflector 28, is located at the base station 24 and projects a beam oflight 30 away from the base station, and in particular away from a pairof photocells 47 and 48.

The remote control unit 25 includes a housing 32 carrying a linearpolarization filter 33 having its plane in the direction of the arrow34, and a retrodirective reflector 35 which may, for instance, include aplurality of corner reflectors 10 of the type shown in FIG. 1, or aglass-bead reflector of the type illustrated in FIG. 2.

The light beam 30 entering the housing 32 is polarized by the filter 33in the plane of the arrow 34. The polarized beam is reflected by theretrodirective reflector 35 through the filter 33 back to the basestation 24 in the form of a reflected polarized beam 37. While it is notessential that the retrodirective reflector be nondepolarizing, for bestefficiency it is desirable to have the reflector 35 not affectmaterially the plane or degree of polarization of the light incidentupon it.

The beam 37 impinges on a pair of linear polarization filters 40 and 41.If the device 35 were retrodirective in the strictest sense, the filters40 and 41 and lamp 27 would have to be located in the same spot, whichwould not be practical, or the use of an expensive Schmidt-type opticalsystem would become necessary. An undesirably acute retrodirectivity is,however, easily avoided in practice by a less-than-perfect angulararrangement of the plates l2, l3 and 14 of the comer reflectors 10, orby a choice of glass beads 17 for the reflector 16 with a refractionindex of 1.5 or less.

The arrows 44 and 45 are intended to indicate that the filters 40 and 4]are arranged with their polarization planes at right angles to eachother, so that the reflected beam 37 penetrates the filter 40, butcannot pass through the filter 41, when the remote unit 25 is heldginsuch a position that the polarization planes of the filters 33 and 40are parallel to each other.

A photocell 47 is located behind the filter 40, and a photocell 48 islocated behind the filter 41. Each of these photocells has a high darkresistance which is materially decreased by the impingement of light, asis conventional.

The photocells 47 and 48 are connected in a control circuit 50 whichincludes a pair of transistors 51 and 52, base resistors 54 and 55,Zener diodes 7 and 58, relays 60 and 61 with contacts 62 and 63, and asource 65 of electrical power, all connected as shown in FIG. 3.

The operation of the control circuit 50 may be described as follows:

The voltage of the source 65 is equally distributed among theseries-connected photocells 47 and 48 when both of these photocells aredark or are equally illuminated. The Zener diodes 57 and 58 are selectedto have a breakdown voltage higher than one-half the voltage of thesource 65 so that neither transistor 51 nor transistor 52 is renderedconductive as long as the voltage of the source 65 is equallydistributed among the photocells 47 and 48.

If the photocell 47 is illuminated, its resistance decreases rapidly andmost of the voltage of the source 65 appears across the photocell 48 ifthe same is dark at that instant. The breakdown voltage of the Zenerdiode 57 is selected so that the emitter-collector circuit of v the PNPtransistor 51 is rendered conductive when most of the voltage-of thesource 65 appears across the photocell 48 as just described.

Conversely, the breakdown voltage of the Zener diode 58 is selected sothat the emitter-collector circuit of the NPN- transistor 52 is renderedconductive when most of the voltage of the source 65 appears across thephotocell 47, which is the case when the photocell 48 is illuminatedwhile the photocell 47 is dark.

It will now be recognized that the base station 24 incorporates controlmeans capable of effecting a first control function in response toincident light having a first quality of polarization (e.g. polarizationin given plane), and a second control function in response to incidentlight having a second quality of polarization (e.g. polarization in aplane perpendicular to said given plane).

It is a principal feature of the preferred embodiment of the inventionillustrated in FIGS. 3 and 4 that changes between the two controlfunctions are easily effected by a positional change of the remotecontrol unit 25.

This is illustrated with the aid of FIG. 4 which shows selected parts ofthe remote control system depicted in FIG. 3.

According to FIG. 4 the remotecontrol unit is rotated with respect tothe position shown in FIG. 3 by an angle of 90 about an axis 70 whichextends substantially along the light beam 30. In this manner, the planeof polarization of the filter 33 in the unit is displaced by 90 relativeto the plane of polarization of the filter 40. In consequence the planeof polarization of the reflected beam 37 is rotated so that the beam 37penetrates the filter 41 and illuminates the photocell 48, while thephotocell 47 is now dark, since the beam 37 is now polarized at rightangles to the plane of polarization of the filter 40.

It will now be appreciated that either the relay contact 62 or the relaycontact 63 can be remotely closed, depending on the rotational positionof the hand-held unit 25. More specifically, if the unit 25 is in theposition shown in FIG. 3, then the transistor 51 is switched on for anenergization of the relay 61 and a closure of the relay contact 63.Conversely, if the unit 25 is in the position shown in FIG. 4, then thetransistor 52 is switched on for an energization of the relay 60 and aclosure of the relay contact 62.

By way of example, it is assumed that the control system of FIGS. 3 and4 is employed to control a motion picture projector 75 which projectsluminous images from a film (not shown) with the aid of a lens system76. It is further assumed that users of the projector 75 have thefrequent desire to advance the film at a rapid rate for the skipping ofscenes that are not to be displayed during a given performance. It ismoreover assumed that users of the projector 75 have the frequent desireto run film backwards preparatory to a replay of given scenes.

From the mechanical point of view, these functions can easily beperformed by means of adjustable gears which selectively decrease thegear ratio for a rapid film advance, and alternatively reverse thedirection of the film drive. However, it is frequently desirable thatthese functions be controlled remotely by an operator who is seated inthe audience at a location spaced from the projector.

According to FIG. 3, the relay contacts 62 and 63 are connected to acontrol 78 that may have the requisite solenoids (not shown) foractuating the above-mentioned gears in the film drive. For instance,closure of the relay contact 63 may result in actuation of the fastforward film motion, while closure of the relay contact 62 may result inactuation of the film reversal mode.

Accordingly, if the remote control unit 25 is held in the rotationalposition shown in FIG. 3 and is then moved into the beam 30, thepolarized reflected beam 37 will cause closure of the relay contact 63and fast forward motion of the film in response to illumination of thephotocell 47. If the fast forward motion is desired to be stopped, theunit 25 is simply moved out of the trajectory of the beam 30 whereuponnormal film advance may resume.

Similarly, if the remote control unit 25 is held in the rotationalposition shown in FIG. 4 and is then moved into the beam 30, thepolarized reflected beam 37 will cause closure of the relay contact 62and reverse motion of the film in response to illumination of thephotocell 48. This reverse film motion may thereupon be stopped byremoval of the unit 25 from the trajectory of the beam 30.

It will now be recognized that the principles of the subject inventionlead to a remote control unit that is inexpensive, very simple, and easyto actuate. If the unit is rectangular in cross section, having forinstance a width greater than its height, it is particularly easy forthe operator to memorize and bring about in the dark the particularposition of the remote control unit 25 for the realization of a desiredmode of operation.

This principle is illustrated in FIG. 5 in which a preferred form ofremote control unit is shown in perspective.

According to FIG. 5, the housing 32 has a cross section extendingthrough the axis of rotation 70 and having a greater dimension in onedirection than in another direction at right angles to said onedirection. By way of example, the housing 32 has a width 80 greater thanits height 81. In this manner, the user of the remote control unit 25will be able to know in the dark how he has to hold the unit for adesired effect. To aid his memory, markings or lettering 82 and 83 maybe provided on the housing 32, such as an R" for film reversal, and an FF" for fast forward drive of the film.

If desired, the projector 75 may be used in lieu of the lamp 27 as alight source for the control system. In this case, the photocells 47 and48 are so arranged that the filters 40 and 41 are illuminated by lightreflected and polarized by the remote control unit 25 if this unit isheld by its user into at least fringe areas of the beam 85 emitted bythe projector 75. In this case, the control system can be operated withthe visible light emitted by the projector.

'If visible light emitted by the lamp 27 is objectionable, invisiblelight may be used. By way of example, the lamp 27 maybe provided with aninfrared filter 87 which renders the beams 30 and 37 infrared and thusinvisible, provided the lamp 27 is of a type that emits a component inthe infrared region, as is the case with most incandescent lamps.

Various polarizers are suitable for the filters 33, 40 and 41. Preferredfor present purposes are sheet polarizers based on inventions by Dr. E.H. Land and sold by the Polaroid Corporation under its registeredtrademark Polaroid." Early types of these sheet polarizers includeduniform dispersions of uniformly oriented acicular synthetic dichroiccrystals,

' notably crystals of herapathite (quinine sulfate periodide), in

a matrix of cellulose acetate. Currently manufactured-sheet polarizerscomprise the commercially available I-I-type, including orientedpolyvinyl alcohol sheets imbibed with iodine, and thecommercially-available K-type, including an oriented polyvinylene.

Polarizers suitable for infrared work include sheet polarizersmanufactured with an increased iodine concentration on polyvinyl alcoholand with a heating of the polyvinyl alcohol matrix before stretching.,The lamp filter 87 is then preferably selected to pass radiations inthe near-infrared range, such as a range between visible red and about-2microns.

FIG. 6 shows an important modification of the system of FIGS. 3 and 4,in accordance with a further preferred embodiment of the subjectinvention. Like reference numerals among FIGS. 3, 4 and 6 designate likeor functionally equivalent parts. 1

According to FIG. 6, the retrodirective reflector 35 is mounted on arotatable shaft 90 having a pinion 91 coupled thereto. A rack 92 engagesthe pinion 91 and is arranged and biased by a spring 93 so that theretrodirective reflector 35 has a rest position in which it extends atright angles to the polarizer filter 33. The reflector 35 carries ablind 95 which masks the reflector-35 against incident light when thesame is in its illustrated rest position. this manner, no light isreflected by the reflector 35 until a button 96, which is mounted on therack 92, is depressed so that the reflector 35 swings about the axis 90in the direction of the arrow 98, until it extends parallel to thepolarizer filter 33.

The light retrodirected by the reflector 35 when the same is locatedparallel to the filter 33 is again polarized by such filter 33, and theresultingpolarized beam 37 impinges on the filters 40 and 41 of thephotocells 47 and 48. As before, the control 50 at the base station 24causes closure of the contact 63 in response to illumination of thephotocell 47 through the filter 40, and closure of the contact 62 inresponse to illumination of the photocell 48 through the filter 41.

The photocell 47 is illuminated when the remote control unit is in theposition illustrated in FIG. 6 (note direction of arrow 34) and when thebutton 96 is depressed. Conversely, the photocell 48 is illuminated whenthe remote control unit is in the position illustrated in FIG. (noterotated position of arrow 34) and when the button 96 is depressed.

By way of example, it is assumed that the control system of FIG. 6serves to selectively energize and deenergize an appliance and to selectpredetermined modes of operation of the appliance. For instance, thecontrol system of FIG. 6 may be employed to control an on-off switch 100and a channel selector 102 of a television set (not shown). To this end,the contact 62 is connected to a bistable" device, such as a flip-flopstage 103, which alternatively closes and opens the switch 100 inresponse to successive closures of the switch 62. The contact 63 isconnected to a source 1050f electric power and to a stepping motor 106.

The stepping motor 106 has an armature 108 which incrementally drives aratchet wheel 109 through a dog and pawl arrangement 110. The ratchetwheel 109 is coupled to the channel selector 102 for advancing theselector by one channel in response to an advancement of the ratchetwheel by one step.

The lamp 27 with reflector 28, and preferably with the infrared filter87, may as shown in FIG. 3 and as explained above be located in thevicinity of the photocells 47 and 48.

If it is desired to actuate the switch to its on position,

;the remote control unit 25 is held into the beam 30 in the rotationalpositions shown in FIG. 4, and the button 96 (see FIG. 6) is depressedso that the reflector 35 is swung into position for a reflection of thebeam onto the filters 40 and 41. The then prevailing polarization of thereflected 'beam 37 causes the photocell 48 to be illuminated. This inturn, closes the contact 62 so that the bistable circuit 103 isenergized to turn the switch 100 to its on" position, in which positionit remains after the button 96 has been released.

The remote control unit 25 is then rotated about the axis 70 to theposition shown in FIG. 6. In that position the photocell 47 isilluminated through the filter 40 when the button 96 is depressed toswing the reflector 35 in the direction of the arrow 98. Illumination ofthe photocell 47 causes closure of the contact 63, which connects thesource to the stepping motor 106. In consequence, the channel selector102 is advanced by one channel. The button 96 in the remote unit 25 maythen be released.

If desired, the button 96 may be depressed and released several timeswhile the unit '25 is held in the beam 30as shown in FIG. 6. Thisresults in a pulsing of the reflected and polarized beam 37 and in anadvance of the channel selector 102 by as many channels as there areactuations ofthe button 96.

The switch is actuated to its off position by an insertion of the unitinto the beam 30 in the rotational position 'shown in FIG. 4, and by adepression of the button 96.

Several modifications of the control system of FIG. 6 are apparent onceits underlying principle has been understood. For instance, thereflector 35 could be mounted in the rear of the unit as shown in FIGS.3 and 4, and a blind could be mounted on the pinion 91 so as to be in avertical position obscuring the reflector when the button is in theillustrated released state, and to swing to a horizontal positionpermitting redirection of the beam 30 by the reflector when the buttonis depressed. In this case, the reflected and polarized beam 37 would bepulsed by movement of the blind relative to the reflector, rather thanby movement of the reflector.

Moreover, a further selector and stepping motor combination similar tothe selector 102 and stepping motor 106 could be connected to thecontact 62 in substitution to the flip-flop 103 and on/off switch 100.This further selector and stepping motor combination could then, forinstance, serve the selection of ultra-high frequency channels, whilethe selector 102 and stepping motor 106 could serve the selection ofvery-high frequency channels of a television set.

Yet another preferred embodiment of the invention is shown in FIG. 7where like reference numerals as among FIGS. 3, 4 and 7 indicate like orfunctionally equivalent parts.

According to FIG. 7 the light beam 30 is polarized by a linear polarizerin a plane extending parallel to either the plane of polarization of thephotocell filter 40 or the plane of polarization of the photocell filter41. The filter 120 may be of the same material as the filter 33, 40 or41, and an infrared filter 87 may or may not be combined with the lamp27 depending on whether operation with visible light or with invisiblelight is desired.

The remote control unit in FIG. 7 is equipped with phase retardationmeans in the form of a quarter-wave retardation plate 122 in lieu of thepreviously described linear polarizer 33. The linearly polarized beam 30traverses the quarter-wave plate 122 twice; namely, once when enteringthe unit 25 and a second time after retrodirection by the reflector 35.In this manner, the plane polarized light of beam 30 is reflected withan effective retardation of one-half wavelength in beam 37. As a result,the plane of polarization of the beam 30 is rotated by 90 by the remotecontrol unit 25 including the retrodirective reflector 35 and thequarter-wave retardation plate 122.

In this manner the reflected beam 37 may be made to illuminate thephotocell which is associated with the polarizer whose plane ofpolarization extends at right angles to the plane of polarization of thepolarizer120. By way of example, if the polarization plane of the lampfilter 120 extends parallel to the polarization plane of the photocellpolarizer 40, then the reflected beam 37 will illuminate the photocell48 behind the polarizer 41 upon direction and rctrodirection of lightfrom the beam through the retardation plate 122.

Cessation of illumination of the photocell 48 by the beam 37 andillumination of the photocell 47 through the polarizer 40 by that beammay thereupon be brought about by removal of the retardation plate 122from the path of the beam 30 and the path of reflected beam 37, at leastfor all practical purposes. By way of example, the retardation plate 122may be mounted on a mechanism similar to that shown in FIG. 6 at 90, 91,92, 93 and 96 so that the retardation plate may be swung to a positionshown in FIG. 7 by dotted lines 125 upon actuation of a button. To thisend, the plate 122 may for instance be so mounted on a shaft 90 that itextends vertically when a button 96 is released, and is swunghorizontally as indicated at 125 when the button 96 is depressed.

In the latter case, the plane of polarization of the beam 30 is notrotated by the remote control unit, and the photocell 47 is illuminatedthrough the polarizer 40.

Alternatively, the retardation plate" 122 may be retained in a verticalposition and rotated by 4'5 so that the plane of polarization of thereflected beam 37 is rotated by 90 whereby the reflected beam 37 iscaused to illuminate the photocell 47 through the polarizer 40.

Accordingly, the system of FIG. 7 again permits selective actuation ofthe contacts 62 and 63, for the execution of distinct control functions,in response to distinct manipulations of the remote control unit 25. Ifdesired, the principle illustrated in FIG. 6 may be employed in FIG. 7to provide a system operating with pulsed reflected beams.

Quarter-wave retardation plates of the type used at 122 are well knownin the light polarization art and are typically sheets of transparentanisotropic material, such as mica or stretched plastic film, displayingtwo different refractive indices producing in response to incident lighttwo emerging rays having a phase difference of IT/2.

It will now be recognized that the system of FIG. 7 broadly representsan embodiment of the subject invention in which the means 27 and 28 forprojecting the light beam 30 have operatively associated therewith means120 for polarizing the beam of light 30 in a predetermined plane, and inwhich the remote unit 25 includes means and 122 for selectively rotatingthe polarization of the light beam 30 in parallel to the plane ofpolarization of the filter and alternatively in parallel to the plane ofpolarization of the filter 41. i

I claim: 1. Remote control system comprising: means for sensing incidentlight having a first quality of polarization and incident light having asecond, quality of polarization;

control means connected to said sensing means for effecting a firstcontrol function in response to sensed incident light having said firstquality of polarization, and a second control function in response tosensed incident light having said second quality of polarization; meansfor projecting a beam of light in a direction away from said sensingmeans; and I a portable remote unit including means for reflecting saidbeam of light to said sensing means and means combined in said remoteunit with said reflecting means for selectively imparting on said beamof light said first quality of polarization and alternatively saidsecond quality of polarization.

2. Remote control system as claimed in claim 1, wherein:

said beam of light is a beam of invisible radiation.

3. Remote control system as claimed in claim 1, wherein:

said beam of light is a beam of infrared radiation.

4. Remote control system as claimed in claim 1, wherein:

said remote unit includes reflector means for said beam of light, andlight polarization means combined with said reflector means andconstructed to selectively impart on said beam of light said firstquality of polarization and alternatively said second quality ofpolarization.

5. Remote control system as claimed in claim 1, wherein:

said projecting means are located adjacent said sensing means; and

said remote unit includes substantially retrodirective reflector meansfor said beam of light, and light polarization means combined with saidreflector means and constructed to selectively impart on said beam oflight said first quality of polarization an alternatively said secondquality of polarization.

6. Remote control system as claimed in claim 5, wherein:

said beam of light is a beam of invisible radiation.

7. Remote control system as claimed in claim 5, wherein:

said beam of light is a beam of infrared radiation.

8. Remote control system as claimed in claim 1, wherein:

said sensing means include means for sensing incident light polarized ina first plane, and incident light polarized in a second plane;

said control means include means for effecting said first controlfunction in response to sensed incident light polarized in said firstplane, and said second control function in response to sensed incidentlight polarized in said second plane; and

said remote unit includes a combination of substantially retrodirectivereflector means and light polarization means for selectively polarizingsaid beam of light in said first plane and for reflecting said beam oflight polarized in said first plane to said control means for initiationof said first control function, and for alternatively polarizing saidbeam of light in said second plane and for reflecting said beam of lightpolarized in said second plane to said control means for initiation ofsaid second control function.

9. Remote control system as claimed in claim 8, wherein:

said remote unit includes a portable housing containing saidretrodirective reflector means, and said light polarization meansinclude a linear polarization filter mounted in said housing forpolarizing said beam of light in said first plane when said housing isheld in at least one rotational position, and for polarizing said beamof light in said second plane when said housing is held in at leastanother rotational position displaced from said one rotational positionby a predetermined angle.

10. Remote control system as claimed in claim 9, wherein:

said second plane is displaced from said first plane by an angle of andsaid predetermined angle of rotational position displacement is 90.

11. Remote control system as claimed in claim 10, wherein:

said housing has a first dimension in a first direction perpendicular tosaid beam of light, and a second dimension in a second directionperpendicular to said beam of light and to said first direction, withone of said first and second dimensions being greater than the other ofsaid first and second dimensions to facilitate the orientation of saidhousing into any one of said rotational positions.

12. Remote control system as claimed in claim 10, wherein:

said housing has a width greater than its height to facilitate theorientation of said housing into angular positions displaced from eachother by 90.

13. Remote control system as claimed in claim 1, wherein:

said first control function includes several first control operations,and said second control function includes several second controloperations;

said control means are constructed to selectively effect said firstcontrol operations in response to sensed pulsed incident light having afirst quality of polarization, and to selectively effect said secondcontrol operations in response to sensed pulsed incident light having asecond quality of polarization;

said remote unit includes means for selectively pulsing said beam oflight having said first quality of polarization and alternatively saidsecond quality of polarization; and

said sensing means include means for sensing said pulsed beam of lighthaving said first quality of polarization and alternatively said secondquality of polarization.

147 Remote control system comprising:

means for sensing incident light having a first quality of polarizationand incident light having a second quality of polarization; 1

control means connected to said sensing means for effecting a firstcontrol function in response to sensed incident light having said firstquality of polarization, and a second control function in response tosensed incident light having said second quality of polarization;

means for projecting in a direction away from said sensing means a beamof light polarized in a predetermined plane;

and

a portable remote unit including means for reflecting said polarizedbeam of light to said control means and means combined in said remoteunit with said reflecting means for selectively realizing in saidreflected beam of light said first quality of polarization andalternatively said second quality of polarization.

15. Remote control system as claimed in claim 14, wherein:

said sensing means include means for sensing incident light polarized ina first plane, and incident light polarized in a second plane;

said control means include means for effecting said first controlfunction in response to sensed incident light polarized in a firstplane, and said second control function in response to sensed incidentlight polarized in a second plane; and

said remote unit includes means for selectively reflecting said beam oflight with a polarization in said first plane and alternativelyreflecting said beam of light with a polarization in a second plane.

16. Remote control system as claimed in claim 15, wherein:

said projection means are constructed to polarize said projected beam oflight in said first plane; and

said remote unit includes means for selectively rotating thepolarization of said beam of light to said second plane.

17. Remote control system as claimed in claim 16, wherein:

said selective rotation means include phase retardation means.

18. Remote control system as claimed in claim 16, wherein:

said selective rotation means include a quarter-wave retardation plate.

19. Remote control system as claimed in claim 15, wherein:

said beam of light is a beam of invisible radiation.

20. Remote control system as claimed in claim 15, wherein:

said beam of light is a beam of infrared radiation.

1. Remote control system comprising: means for sensing incident lighthaving a first quality of polarization and incident light having asecond quality of polarization; control means connected to said sensingmeans for effecting a first control function in response to sensedincident light having said first quality of polarization, and a secondcontrol function in response to sensed incident light having said secondquality of polarization; means for projecting a beam of light in adirection away from said sensing means; and a portable remote unitincluding means for reflecting said beam of light to said sensing meansand means combined in said remote unit with said reflecting means forselectively imparting on said beam of light said first quality ofpolarization and alternatively said second quality of polarization. 2.Remote control system as claimed in claim 1, wherein: said beam of lightis a beam of invisible radiation.
 3. Remote control system as claimed inclaim 1, wherein: said beam of light is a beam of infrared radiation. 4.Remote control system as claimed in claim 1, wherein: said remote unitincludes reflector means for said beam of light, and light polarizationmeans combined with said reflector means and constructed to selectivelyimpart on said beam of light said first quality of polarization andalternatively said second quality of polarization.
 5. Remote controlsystem as claimed in claim 1, wherein: said projecting means are locatedadjacent said sensing means; and said remote unit includes substantiallyretrodirective reflector means for said beam of light, and lightpolarization means combined with said reflector means and constructed toselectively impart on said beam of light said first quality ofpolarization an alternatively said second quality of polarization. 6.Remote control system as claimed in claim 5, wherein: said beam of lightis a beam of invisible radiation.
 7. Remote control system as claimed inclaim 5, wherein: said beam of light is a beam of infrared radiation. 8.Remote control system as claimed in claim 1, wherein: said sensing meansinclude means for sensing incident light polarized in a first plane, andincident light polarized in a second plane; said control means includemeans for effecting said first control function in response to sensedincident light polarized in said first plane, and said second controlfunction in response to sensed incident light polarized in said secondplane; and said remote unit includes a combination of substantiallyretrodirective reflector means and light polarization means forselectively polarizing said beam of light in said fIrst plane and forreflecting said beam of light polarized in said first plane to saidcontrol means for initiation of said first control function, and foralternatively polarizing said beam of light in said second plane and forreflecting said beam of light polarized in said second plane to saidcontrol means for initiation of said second control function.
 9. Remotecontrol system as claimed in claim 8, wherein: said remote unit includesa portable housing containing said retrodirective reflector means, andsaid light polarization means include a linear polarization filtermounted in said housing for polarizing said beam of light in said firstplane when said housing is held in at least one rotational position, andfor polarizing said beam of light in said second plane when said housingis held in at least another rotational position displaced from said onerotational position by a predetermined angle.
 10. Remote control systemas claimed in claim 9, wherein: said second plane is displaced from saidfirst plane by an angle of 90*, and said predetermined angle ofrotational position displacement is 90*.
 11. Remote control system asclaimed in claim 10, wherein: said housing has a first dimension in afirst direction perpendicular to said beam of light, and a seconddimension in a second direction perpendicular to said beam of light andto said first direction, with one of said first and second dimensionsbeing greater than the other of said first and second dimensions tofacilitate the orientation of said housing into any one of saidrotational positions.
 12. Remote control system as claimed in claim 10,wherein: said housing has a width greater than its height to facilitatethe orientation of said housing into angular positions displaced fromeach other by 90*.
 13. Remote control system as claimed in claim 1,wherein: said first control function includes several first controloperations, and said second control function includes several secondcontrol operations; said control means are constructed to selectivelyeffect said first control operations in response to sensed pulsedincident light having a first quality of polarization, and toselectively effect said second control operations in response to sensedpulsed incident light having a second quality of polarization; saidremote unit includes means for selectively pulsing said beam of lighthaving said first quality of polarization and alternatively said secondquality of polarization; and said sensing means include means forsensing said pulsed beam of light having said first quality ofpolarization and alternatively said second quality of polarization. 14.Remote control system comprising: means for sensing incident lighthaving a first quality of polarization and incident light having asecond quality of polarization; control means connected to said sensingmeans for effecting a first control function in response to sensedincident light having said first quality of polarization, and a secondcontrol function in response to sensed incident light having said secondquality of polarization; means for projecting in a direction away fromsaid sensing means a beam of light polarized in a predetermined plane;and a portable remote unit including means for reflecting said polarizedbeam of light to said control means and means combined in said remoteunit with said reflecting means for selectively realizing in saidreflected beam of light said first quality of polarization andalternatively said second quality of polarization.
 15. Remote controlsystem as claimed in claim 14, wherein: said sensing means include meansfor sensing incident light polarized in a first plane, and incidentlight polarized in a second plane; said control means include means foreffecting said first control function in response to sensed incidentlight polarized in a first plane, and said second control function inresponse to sensed incident light polarized in a second plane; and saidremote unit includes means for selectively reflecting said beam of lightwith a polarization in said first plane and alternatively reflectingsaid beam of light with a polarization in a second plane.
 16. Remotecontrol system as claimed in claim 15, wherein: said projection meansare constructed to polarize said projected beam of light in said firstplane; and said remote unit includes means for selectively rotating thepolarization of said beam of light to said second plane.
 17. Remotecontrol system as claimed in claim 16, wherein: said selective rotationmeans include phase retardation means.
 18. Remote control system asclaimed in claim 16, wherein: said selective rotation means include aquarter-wave retardation plate.
 19. Remote control system as claimed inclaim 15, wherein: said beam of light is a beam of invisible radiation.20. Remote control system as claimed in claim 15, wherein: said beam oflight is a beam of infrared radiation.